Process for covering metals or alloys with layers of metallic beryllium



Patented Apr. 21, 1931 UNITED STATES PATENT OFFICE HELLMUT FISCHER, 0FBERLIN-FRIEDEN'AU, GER-MANY, ASSIGNOR, BY MESNE ASSIGN- MENTS, TOMETAL.& THERMIT' CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF NEWJERSEY PROCESS FOR COVERING METALS OR ALLOYS WITH LAYERS 0F METALLICBERYLLIUM No Drawing. Application filed October 3, 1927, serial No.223,836, and in Germany August'20, 192G.

My invention relates to a process for c'overing metals or alloys withlayers of metallic beryllium.

It is well known to produce coatings of aluminium or aluminium alloys byimmersing the article to be coated in the melt of a sa t of the coatingmetal as free as possible from water and electrolyzing the melt or fusedsalt with the aid of soluble anodes of the coating metal, the article tobe covered being connected as the cathode. This well known process is,however, not applicable to the production of perfect coatings ofmetallic beryllium or beryllium alloys, because it is necessary forthis, purpose first to determine the correct temperature at which theelectrolysis of the melt is to take place as well as the correctcomposition of the melt.

It is furthermore impossible to employ in this case soluble anodes as inthe aluminium coating process mentioned above.

There is also known a process for producing tin or zinc coatings uponiron or steel articles for the purpose of preventing rust-.

ing or corrosion, by electrolyzing a melt. Apart from the fact that thisprocess has a difi'erent object, it is also for the reasons specifiedabove not directly applicable for producing perfect coatings ofberyllium by means of electrolysis of a melt.

It is also well knownto separate beryllium in solid form by theelectrolysis of a melt consisting of a beryllium-containing mixture ofsalts. Experiments have proved that this process is not directlyapplicable for the production of coatings of metallic beryllium uponarticles of metal or metal alloys.

There existed thus up to now no process by means of which coatings orcoverings of metallic beryllium useful for vengineering purposes couldbe produced-in a technical manner. i

According to my invention thisproblem is solved b immersing the articlein a melt produce by the application of heat and which consists of atleast one halide of an alkali metal or of an alkaline earth metal and aberyllium compound and electrol n this melt with the article to be coateCOD.-

nected as the cathode. It is essential that the temperature ofthe'bathbe kept during the electrolysis below the fusing point of thearticle to be coated. Preferably the blast of cold air or gas issufiicient to keep,

their temperature lower, for instance about 100 O., lower than thetemperature of the melt.

The character of' the beryllium coating may be modified orimproved bycarrying out the electrolysis at a temperature either slightly or farbelow the fusing point of the article to be coated. The deposited layeris then always smooth, very dense and adheres firmly to the metallicsurface. Generally it is's'uflicient to maintain the electrolysis duringa few seconds only. Should it, however, be desired to obtain a moresubstantial coating of beryllium the duration of the electrolysis may becorrespondingly extended, for instance up to a few minutes. Parts of themelted salt or a light film of oxides which may happen to adhere to thedeposited layer may be removed by sudden immersion into a cooling liquidor mechanically by carefulscr'aping, bufling or the like. The extremelyhard beryllium coating is smooth and firmly adheres to the metallicsurface. According to the difference between the temperature at whichthe electrolysis coated. In this case the deposited metal diffuses moreor less deeply into the base metal and may even form an alloy with it.This layer of alloy is then particularly strong and sion it imparts tothe surface of the coated metal or metal alloy the characteristicqualities of pure beryllium alloys with such metals, such as greathardness, imperviousness to corrosion and so on.

If, on the other hand, it is desired to obtain layers of pure beryllium,the process is referably carried through at temperatures of the bathwhich lie as far as possible below the fusing point of the metal to becovered. The desired temperature ratio may be attained by an appropriatecooling of the article to be coated and connected as the cathode. Inthis case there is formed upon the base metal a surface coating of pureberyllium which is of great hardness andadheres firmly,'but does notalter the characteristic qualities ofthe foundation metal.

The best results were obtained upon metals of not too low a fusingpoint, such as aluminium, copper, iron and the like. My improved processmay, however, also be employed for numerous other metals or metalalloys. As suitable electrolytes for the production of berylliumcoatings the halides of beryllium are used with special advantage.According to the nature of the metal to be coated the fusing point ofthe melt used may be varied by adding to the beryllium compound orcompounds one or more halides of the alkali metals or of the alkalineearth metals.

As an example of my improved process I will now describe the productionof a deposit of beryllium upon an article of copper. Sodium'fluoride andberyllium fluoride are mixed in the proportion of their molecularweights and the mixture is fused or melted in a crucible of graphiteheated externally. The copper article to be coated is then immersed asthe cathode into the liquid mixture and the graphite crucible isconnected as the anode. After a short time, for instance after a fewseconds, a dense and very firmly adhering coating of metallic berylliumor a copper-beryllium alloy is obtained which by careful bufiing orscraping may be cleaned from any adhering. traces of the salt.

If it is desired to modify or improve the physical properties of theberyllium coating so deposited, and particularly its hardness, theprocess is conducted as follows: a layer of another metal is firstdeposited upon the article to be coated, for instance by electrolysis inan aqueous bath. For such an intermediate layer metals are particularlysuitable which on the one hand adhere firmly to the base metal due tosurface diffusion and on the other hand have the property of absorbingberyllium. Metals such as iron, copper and mckel are particularlysuitable for this intermediate layer. A plurality of such intermediatelayers may be provided.

After such an intermediate layer complying with the specified conditionshas been applied to the article, the article is covered with berylliumin the manner described above by electrolyzing the fused salts.

The following may serve as examples for the application of the lastdescribed process:

1. Upon an article of tungsten there is first deposited a layer of iron,for instance by the electrolysis of an aqueous solution of an iron salt,and upon this layer beryllium is deposited by the electrolysis of a meltkept liquid by heating to about 1200 0., the above specified temperatureconditions being carefully observed.

2. Articles of molybdenum may first be galvanically plated with copper.The beryllium coating is then applied to this copper layer in the abovedescribed manner at a temperature of the bath of 700 to 800 C.

3. Articles of tantalum may first be galvanically nickel-plated. Thesubsequent deposition of the coating of beryllium may preferably takeplace at a temperature of the bath of about 1100 C.

In a similar manner intermediate layers may be produced upon vanadium,niobium and so on before the final coating of beryllium is applied tothem. Generally speaking such intermediate layers are advisable for suchmetal articles as melt considerably above the fusing point of beryllium(about 1285 C.). It will be understood that such intermediate layers mayequally well be applied to articles which consist of alloys.

Various modifications and changes may be made without departing from thespirit and the scope of the invention, and I desire, therefore, thatonly such limitations shall be placed thereon as are imposed by theprior art. It will be understood that for the purpose of my presentinvention, the halide of an alkaline earth metal is to be considered theequivalent of the halide of an alkali metal, and the appended claims areto be interpreted as covering such equivalent.

I claim as my invention 1. The process of producing a permanentlyadhering coating of a beryllium allo upon a metal article having asurface whicl i readily alloys with beryllium, which consistsin'preparing a melt of a sodium fluoride and beryllium fluoride keptliquid by the application of heat, immersing in said melt the article tobe coated, connected as the cathode, and electrolyzing said melt withthe aid of an insoluble anode whilemaintaining the melt at a temperaturewhich lies below the fusing point of beryllium and slightly below thefusing point of the said article.

2. In the production of a permanently adhering coating of a berylliumalloy upon a metal article, the process which comprises depositing alayer of a metal alloying with beryllium upon the article to be coated,preparing a melt from a beryllium halide and at least one alkali metalhalide, maintaining said melt liquid by the application of heat and at atemperature slightl below the fusing point of said .article and elow thefusing Eomt of beryllium, immersing the article earing the said metallayer deposited thereon in said melt, the said article being connectedas the cathode, and electrolyzing the said melt with the aid of aninsoluble anode.

testimony whereof I afiix my signature.

HELLMUT- FISCHER.

